Moonshot chassis 4 is in hwdown

Many machines in this chassis are in hwdown due to presumed multicast issues during frisbee. We've tried rebooting the chassis manager, the chassis switch, and @hibler has power-cycled the whole chassis and re-seated the switch. None of these have done anything, and there are no obvious errors on either the chassis switch or in various boss logs. I've placed the rest of them in hwdown pending further investigation into the issue.